score = int(input("请输入成绩："))

if score >= 70:
    grade = "A+"
elif score >= 67:
    grade = "A"
elif score >= 64:
    grade = "B+"
elif score >= 61:
    grade = "B"
elif score >= 58:
    grade = "B-"
elif score >= 55:
    grade = "C+"
elif score >= 52:
    grade = "C"
elif score >= 49:
    grade = "C-"
elif score >= 46:
    grade = "D+"
elif score >= 43:
    grade = "D"
else:
    grade = "F"

print("等级为：" + grade)